Text Changed Event on Ajax HTML Editor Extender Control Textbox

Java Script to be Used :

<script type="text/javascript">
function onContentsChange12() 
        {
            //document.getElementById('Labeld21').innerText = document.getElementById('TextBoxd21').value;
    var inputText = document.getElementById('TextBoxd12').value;
    var returnText = "" + inputText;
        //-- remove BR tags and replace them with line break
    returnText=returnText.replace(/<br>/gi, "\n");
    returnText=returnText.replace(/<br\s\/>/gi, "\n");
    returnText=returnText.replace(/<br\/>/gi, "\n");

    //-- remove P and A tags but preserve what's inside of them
    returnText=returnText.replace(/<p.*>/gi, "\n");
    returnText=returnText.replace(/<a.*href="(.*?)".*>(.*?)<\/a>/gi, " $2 ($1)");

    //-- remove all inside SCRIPT and STYLE tags
    returnText=returnText.replace(/<script.*>[\w\W]{1,}(.*?)[\w\W]{1,}<\/script>/gi, "");
    returnText=returnText.replace(/<style.*>[\w\W]{1,}(.*?)[\w\W]{1,}<\/style>/gi, "");
    //-- remove all else
    returnText=returnText.replace(/<(?:.|\s)*?>/g, "");

    //-- get rid of more than 2 multiple line breaks:
    returnText=returnText.replace(/(?:(?:\r\n|\r|\n)\s*){2,}/gim, "\n\n");

    //-- get rid of more than 2 spaces:
    returnText = returnText.replace(/ +(?= )/g,'');

    //-- get rid of html-encoded characters:
    returnText=returnText.replace(/&nbsp;/gi," ");
    returnText=returnText.replace(/&amp;/gi,"&");
    returnText=returnText.replace(/&quot;/gi,'"');
    returnText=returnText.replace(/&lt;/gi,'<');
    returnText=returnText.replace(/&gt;/gi,'>');
    //-- return
    document.getElementById('Labeld12').innerHTML = returnText;
        }
</script>

paste this in header section and then write below code in body tag

<ajt:HtmlEditorExtender ID="HtmlEditorExtenderd12" runat="server" 
            TargetControlID="TextBoxd12" EnableSanitization="false"  OnClientChange="onContentsChange12">
            
        </ajt:HtmlEditorExtender>